Post on 16-Jan-2016
Lecture Exam 2Lecture Exam 2Material represented from chapters Material represented from chapters corresponding to corresponding to ALLALL Nervous System Nervous System PhysiologyPhysiology
Nervous System Physiology: Nervous System Physiology: – Intro., Resting Membrane Potential Intro., Resting Membrane Potential Ch. 5 (156-162)Ch. 5 (156-162)– Nerve Impulse Conduction Nerve Impulse Conduction Ch. 8Ch. 8 – Central Nervous Sys. (Functional Regions) Central Nervous Sys. (Functional Regions) Ch. 9Ch. 9– Sensory Physiology Sensory Physiology Ch. 10Ch. 10 – Peripheral Nervous Sys. (ANS & SNS) Peripheral Nervous Sys. (ANS & SNS) Ch. 11Ch. 11
Stop at Muscle Physiology. Stop at Muscle Physiology.
Chapter 10Chapter 10
Sensory PhysiologySensory Physiology
Perception and Sensation Perception and Sensation
PerceptionPerception = = interpretation of interpretation of sensation, sensation, utilizing regions utilizing regions of the brainof the brain
Sensation = Sensation = conscience conscience awareness of a awareness of a stimulus event stimulus event detected by detected by sensory sensory receptorsreceptors
Figure 10-4: Sensory pathways
Sensory Receptor TypesSensory Receptor TypesChemoreceptorsChemoreceptors– Respond to Respond to
chemical ligandschemical ligands
MechanoreceptorsMechanoreceptors– Respond to various Respond to various
forms of forms of mechanical NRGmechanical NRG
PhotoreceptorsPhotoreceptors– Respond to lightRespond to light
ThermoreceptorsThermoreceptors– Respond to Respond to
temperaturetemperature
NociceptorsNociceptors– Respond to painRespond to pain
Figure 10-1: Sensory receptors
Sensory Transduction Converts Sensory Transduction Converts Stimuli into Graded PotentialsStimuli into Graded Potentials
Transduction = conversion of stimulus NRG into info..that can be Transduction = conversion of stimulus NRG into info..that can be processed by the nervous systemprocessed by the nervous system
Adequate stimulus = NRG form to which receptors respond Adequate stimulus = NRG form to which receptors respond – i.e. light, temp., pain, mechanical NRG, ect.)i.e. light, temp., pain, mechanical NRG, ect.)
Threshold stimulus = the minimum stimulus required to activate a Threshold stimulus = the minimum stimulus required to activate a receptorreceptor
Generator potentialGenerator potential– = graded potentials whose amplitude is proportional to the = graded potentials whose amplitude is proportional to the
strength of the stimulusstrength of the stimulusI.E. stronger stimulus, stronger generator potentialI.E. stronger stimulus, stronger generator potential
If generator potential reaches threshold, it initiates an action If generator potential reaches threshold, it initiates an action potential that travels along the sensory neuron to the CNSpotential that travels along the sensory neuron to the CNS
Sensory AdaptationSensory Adaptation= reduction in sensitivity in the presence of a = reduction in sensitivity in the presence of a constant stimulus caused by a decreased constant stimulus caused by a decreased generator potential thus causing a generator potential thus causing a decreased decreased number of action potentials per secondnumber of action potentials per second sent over sent over the sensory neuron the sensory neuron decreased perception of decreased perception of sensationsensation
Phasic receptors Phasic receptors rapidly adapting rapidly adapting
Tonic receptors Tonic receptors slow adapting or do not adapt slow adapting or do not adapt
Pain, vision, & proprioception DO NOT adaptPain, vision, & proprioception DO NOT adapt
Receptive Fields of NeuronsReceptive Fields of NeuronsFig. 10-2 Receptor fields of sensory neurons
Convergence of primary sensory neurons allows simultaneous subthreshold stimuli to sum at the secondary sensory neuron and initiate an action potential.
Convergence of primary sensory neurons allows simultaneous, subthreshold stimuli to sum at the secondary sensory neuron & initiate an action potential.
Two-Point DiscriminationTwo-Point Discrimination
Figure 10-3: Two-point discrimination
Somatic PathwaysSomatic PathwaysFigure 10-9: Sensory pathways cross the body’s midline
Somatic Senses Somatic Senses Figure 10-10: The somatosensory cortex
Free nerve endingsFree nerve endings
Cold receptorsCold receptors– detect detect lossloss of heat (stimuli of heat (stimuli belowbelow body temp.) body temp.)
Warm receptorsWarm receptors– detect detect gaingain of heat (stimuli of heat (stimuli aboveabove body temp.) body temp.)
Pain receptorsPain receptors
TemperatureTemperature
NociceptorsNociceptors
Fast painFast pain– sharp, & localizedsharp, & localized– transmitted via alpha-delta (myelinated) fiberstransmitted via alpha-delta (myelinated) fibers
Slow painSlow pain– Duller, more diffuseDuller, more diffuse– Transmitted via C (unmyelinated) fibersTransmitted via C (unmyelinated) fibers
PainPain
Referred PainReferred Pain
Figure 10-13: Referred pain
Chapter 11Chapter 11
Efferent Division : Autonomic Efferent Division : Autonomic (ANS) and Somatic Motor Control (ANS) and Somatic Motor Control
(SNS)(SNS)(Control of Body Systems)(Control of Body Systems)
Autonomic Division: Homeostatic balancingAutonomic Division: Homeostatic balancing
ControlsControls– Smooth & cardiac Smooth & cardiac
muscle muscle – Glands & adiposeGlands & adipose
Antagonistic branchesAntagonistic branches– ParasympatheticParasympathetic
"Rest & digest""Rest & digest"
Restore bodyRestore body
– SympatheticSympathetic““Fright, fight, or flight"Fright, fight, or flight"
Energetic actionEnergetic action
Figure 11-1: Homeostasis and the autonomic division
Autonomic Pathways: Communicate to BodyAutonomic Pathways: Communicate to Body
Figure 11-2: The hypothalamus and brain stem initiate autonomic, endocrine, and behavioral responses
Coordinates Coordinates homeostatic homeostatic responsesresponses– Autonomic Autonomic – Endocrine Endocrine – Behavioral Behavioral
Blood pressureBlood pressureOsmolarityOsmolarityTonic regulationTonic regulationAntagonistic Antagonistic controlcontrolReceptor directed Receptor directed responseresponse
HypothalamusHypothalamus– Water balanceWater balance– TemperatureTemperature– HungerHunger
PonsPons– RespirationRespiration– CardiacCardiac– VasoconstrictionVasoconstriction
MedullaMedulla– RespirationRespiration
Autonomic Control CentersAutonomic Control Centers
Figure 11-3: Autonomic control centers in the brain
Preganglionic Preganglionic neuronneuron– ShortShort– Origin: spinal cordOrigin: spinal cord– NT: cholinergicNT: cholinergic (ACh) (ACh)
GangliaGanglia– Sympathetic chainSympathetic chain– Near spinal cordNear spinal cord– Nicotinic ReceptorNicotinic Receptor
Postganglionic Postganglionic neuronneuron– LongLong– NT: adrenergicNT: adrenergic (NE) (NE)
Comparison of Sympathetic PathwaysComparison of Sympathetic Pathways
Figure 11-7: Sympathetic and parasympathetic pathways
Comparison of Parasympathetic PathwaysComparison of Parasympathetic Pathways
Figure 11-7: Sympathetic and parasympathetic pathways
Preganglionic Preganglionic neuronsneurons– Originate inOriginate in
Brain stemBrain stem
Lower cordLower cord
– NT: cholinergicNT: cholinergic (ACh) (ACh)
GanglionGanglion– Near targetNear target– Nicotinic receptorsNicotinic receptors
Postganglionic Postganglionic neuronneuron– NT: cholinergicNT: cholinergic (ACh) (ACh)
Figure 11-5: Autonomic sympathetic and parasympathetic pathways
VaricositiesVaricosities
NT released to NT released to ECFECF
No cleftNo cleft
ImpactImpact– Large areaLarge area– Slow actingSlow acting– Long durationLong duration
Synapses in Autonomic NervesSynapses in Autonomic Nerves
Figure 11-8: Varicosities of autonomic neurons
Acetylcholine synthesis & recyclingAcetylcholine synthesis & recycling
Figure 8-21: Synthesis and recycling of acetylcholine at the synapse
Norepinephrine Release and RecyclingNorepinephrine Release and Recycling
Figure 11-9: Norepinephrine release at a varicosity of a sympathetic neuron
Autonomic Neurotransmitters
Sympathetic Division Parasympathetic Division
Neurotransmitter Norepinephrine Acetylcholine
Synthesized (made) from
Tyrosine Acetyl CoA + choline
Inactivated by (ENZ) Monoamine oxidase (MAO)
Acetylcholinesterase AChE
ENZ location in Mitochondria of varicosity Synaptic cleft
Varicosity of reuptake Norepinephrine Choline
*Varicosity = swollen regions along autonomic axons that store and release neurotransmitters.
Table 8-4-1: Major Neurocrines
Adrenal Medulla: Adrenal Medulla: A Modified Sympathetic GanglionA Modified Sympathetic Ganglion
Figure 11-10: The adrenal medulla
Sympathetic Sympathetic stimulationstimulation– Catecholamine Catecholamine
release to bloodrelease to bloodEpinephrineEpinephrine
NorepinephrineNorepinephrine
– Travel to:Travel to:Multiple targetsMultiple targets
Distant targetsDistant targets
Receptor Found In Sensitivity Second Messenger
1 Most sympathetic target tissue NE > E Activates phospolipase C
2 Gastrointestinal tract & pancreas NE > E Inhibits cAMP
1 Heart muscle, kidney NE = E Activates cAMP
2 Certain blood vessels and smooth muscle of some organs
E > NE Activates cAMP
NE = Norepinephrine (neurotransmitter) E = Epinephrine (hormone from adrenal medulla)
SENSITIVITY OF PERIPHERAL ADRENERGIC RECEPTORS
TO CATECHOLAMINES
Norepinephrine
1 receptor 2 receptor
Activates Phospholipase
Reduces/Inhibits cAMP levels
Release of Ca+2
Smooth muscle contraction & gland secretion
Smooth muscle relaxation & decrease in
gland secretion
Alpha Receptor Stimulation
Epinephrine
Beta Receptor Stimulation
Activation of adenylate cyclase
cAMP
1 Receptor 2 Receptor
Stimulation of metabolism, cardiac muscle stimulation
Inhibition and relaxation of smooth muscle
in respiratory passageways and in blood vessels
of skeletal muscles
Receptor Agonists (mimics) Antagonists (blockers) Indirect Agonists/Antagonists
Cholinergic Acetylcholine AChE* inhibitors: neostigmine; parathionInhibits ACh release: botulinus toxin
Muscarinic
Muscarine Atropine; scopolamine
Nicotinic Nicotine -bungarotoxin (muscle only), tetraethylammonium (TEA) (ganglia only), curare
Adrenergic Norepinerphrine; Epinephrine
Stimulates NE release: ephedrine, amphediminesPrevents NE uptake: cocaine
Pheylephrine “alpha-blockers”
Isopreterenol “beta-blockers”; propranolol (1 &
2); metoprolol (1 only)
*AChE = acetylcholinesterae
Review of Efferent Pathways: Motor & AutonomicReview of Efferent Pathways: Motor & Autonomic
Figure 11-11: Summary of efferent pathways
COMPARISION OF SNS & ANS
SOMATIC AUTONOMIC
Number of neurons in efferent pathway
1 2
Neurotransmitter/receptor at neuron-target synapse
ACh (nicotinic) ACh (muscarinic) or NE ( or )
Target tissue Skeletal Muscle Smooth and cardiac muscle; some endocrine and exocrine glands; some adipose tissue
Structure of axon terminal regions
Boutons Boutons and varicosities
Effects on target tissue Excitatory only: muscle contracts
Excitatory or Inhibitory
Peripheral components found outside the CNS
Axons only Preganglionic axons, ganglia, postganglionic neurons
Summary of function Posture and movement Visceral function, including movement in internal organs & secretion; control of metabolism
Body movementBody movement
AppendagesAppendages
LocomotionLocomotion
Single neuron Single neuron – CNS originCNS origin– MyelinatedMyelinated
Terminus Terminus – BranchesBranches– Neuromuscular Neuromuscular
junctionjunction
Somatic Motor Division: Controls Skeletal Somatic Motor Division: Controls Skeletal MusclesMuscles
Figure 11-11: Summary of efferent pathways
Neuromuscular Junction: OverviewNeuromuscular Junction: Overview
Figure 11-12: Anatomy of the neuromuscular junction
Terminal Terminal boutonsboutons
Synaptic cleftSynaptic cleft– MatrixMatrix– AChEAChE– Hold togetherHold together
End motor plateEnd motor plate– On muscleOn muscle– Nicotinic Nicotinic
receptorsreceptors
Neuromuscular Junction: Neuromuscular Junction: Mechanism of Signal ConductionMechanism of Signal Conduction
Figure 11-13: Events at the neuromuscular junction
Axon terminalAxon terminal– AP signalsAP signals– ACh releaseACh release
Motor end plateMotor end plate– 2 ACh bind2 ACh bind– opens cation opens cation
channelchannel– Na+ influxNa+ influx– Membrane Membrane
depolarizeddepolarized
Stimulates fiber Stimulates fiber contractioncontraction
Autonomic branches: Autonomic branches: sympathetic and parasympathetic sympathetic and parasympathetic – Regulate glands, smooth & cardiac musclesRegulate glands, smooth & cardiac muscles– Team with endocrine to regulate homeostasis Team with endocrine to regulate homeostasis – Are regulated by hypothalamus, pons & medullaAre regulated by hypothalamus, pons & medulla– Have pathways with 2 neurons and a ganglionHave pathways with 2 neurons and a ganglion– Use varicosities to release NTs Use varicosities to release NTs – Have diverse receptors: tonic & antagonistic Have diverse receptors: tonic & antagonistic
regulationregulation
SummarySummary
Somatic ControlSomatic Control
Efferent motor neurons control skeletal Efferent motor neurons control skeletal musclesmuscles– Single long myelinated neuron from CNS Single long myelinated neuron from CNS – Neuromuscular junction structure & Neuromuscular junction structure &
mechanismmechanism
SummarySummary